Home-built integrated microarray system (IMAS). A three-laser confocal fluorescence scanner coupled with a microarray printer

Abstract

Microarray technology covers the urgent need to exploit the accumulated genetic information from large-scale sequencing projects and facilitate investigations on a genome-wide scale. Although most applications focus on DNA microarrays, the technology has expanded to microarrays of proteins, peptides, carbohydrates, and small molecules aiming either at detection/quantification of biomolecules or investigation of biomolecular interactions in a massively parallel manner. Microarray experiments require two specialized instruments: An arrayer (or printer), for construction of microarrays, and a readout instrument (scanner). We have designed, constructed, and characterized the first integrated microarray system (IMAS) that combines the functions of a microarrayer and a three-laser confocal fluorescence scanner into a single instrument and provides excellent flexibility for the researcher. The three-axis robotic system that moves the printing head carrying multiple pins for arraying is also used for moving the microarray slide in front of a stationary optical system during scanning. Since the translation stages are the most expensive and crucial components of microarray printers and scanners, the proposed design reduces considerably the cost of the instrument and enhances remarkably its operative flexibility. Experiments were carried out at resolutions of 2.5, 5, 10, and 20 μm. The scanner detects 0.128 nmol L−1 carboxyfluorescein (spots with diameters of 70 μm) corresponding to 1.8 molecules μm−2. The linear range extends over 3.5 orders of magnitude (R2 = 0.997) and the dynamic range covers almost five orders of magnitude. DNA microarray model experiments were carried out, including staining with SYBR Green I and hybridization with oligonucleotides labeled with the fluorescent dyes Alexa 488, Alexa 594, and Alexa 633.